Hillary Rodham Clinton may be signaling an intent to run for president in 2016.

Photo: Chip Somodevilla, Getty Images

Hillary Rodham Clinton may be signaling an intent to run for...

Image 2 of 2

This video framegrab, provided by the Human Rights Campaign shows former Secretary of State Hillary Rodham Clinton announcing her support for gay marriage, putting her in line with other potential Democratic presidential candidates on a social issue that is rapidly gaining public approval. Clinton made the announcement in an online video released Monday morning by the gay rights advocacy group Human Rights Campaign. She says in the six-minute video that gays and lesbians are "full and equal citizens and deserve the rights of citizenship." (AP Photo/Human Rights Campaign)

Hillary Rodham Clinton's embrace of same-sex marriage Monday signals she may be seriously weighing a 2016 presidential run and trying to avoid the type of late-to-the-party caution that hurt her first bid.

Her chief Democratic rivals endorsed same-sex marriage as much as seven years ago, and it's widely popular with Democratic and independent voters.

By supporting same-sex marriage a full two years before the next presidential primary warms up, Clinton may render the issue largely settled among Democrats, should she decide to run.

But things could be vastly different in the November 2016 general election, regardless of who wins the Democratic nomination. That nominee is virtually certain to support same-sex marriage, whereas there's a strong possibility the Republican nominee will not.

That could be a problem for the GOP nominee if same-sex marriage becomes a prominent issue. A poll released Monday shows a dramatic shift in attitudes about legalizing same-sex marriage, with 58 percent of Americans now supporting it.

Three years ago, the figure was 47 percent, the ABC News/Washington Post poll reported.

Clinton recently stepped down as secretary of state, freeing her to talk more openly about U.S. domestic political matters. Some Democratic activists cautioned that her Monday statement isn't a sure sign she plans to run for the office that her husband, Bill, won two decades ago.

"I have no idea whether she is going to run or not," said veteran strategist Jim Manley. "All I know is that she was going to have to make this move quickly after stepping down as secretary of state if she was even going to think about it."

As support for same-sex marriage becomes the mainstream position among Democrats, the issue is increasingly divisive among Republicans. Sen. Rob Portman of Ohio last week became the only Republican senator to support legalizing same-sex marriage. He did so after learning that one of his adult sons is gay.

Dozens of prominent Republicans have urged the Supreme Court to overturn the Defense of Marriage Act. But many GOP-controlled states have asked the court to uphold the law.